The current contest is just as close and intense, but the candidates have campaigned in only 10 states since the political conventions. There are towns in Ohio that have received more attention than the entire West Coast.

The shrinking electoral battleground has altered the nature of American self-governance. There is evidence that the current system is depressing turnout, distorting policy, weakening accountability and effectively disenfranchising the vast majority of Americans.

“It’s a new way to run a country,” says Bill Bishop, co-author of “The Big Sort,” a 2008 book that examined the most important cause of the trend: the recent tendency of like-minded people to live near one another.

That demographic shift means the country is now dominated by solidly Democratic states on the coasts and solidly Republican ones in the interior and in much of the South. In a close election, all of those states are completely out of reach for one candidate or the other.